Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$81.56	5.270%	$85.8582	$85.86	$85.85	$85.90
Purchase #2	$70.51	3.319%	$72.8502	$72.85	$72.85	$72.90
Purchase #3	$250.53	11.246%	$278.7046	$278.70	$278.70	$278.70
Purchase #4	$79.89	8.411%	$86.6095	$86.61	$86.60	$86.60
Purchase #5	$116.96	12.840%	$131.9777	$131.98	$132.00	$132.00
Purchase #6	$131.55	11.641%	$146.8637	$146.86	$146.85	$146.90
Purchase #7	$144.36	8.795%	$157.0565	$157.06	$157.05	$157.10
7 purchase totals =	$875.36		$959.9204	$959.92	$959.90	$960.10